This invention relates to implantable electrodes generally and to implantable defibrillation electrodes more particularly.
Over the past 20 years there has been substantial work toward development of a practical, implantable defibrillator. Early conceptions of implantable defibrillators, such as disclosed in U.S. Pat. No. Re. 27,652 by Mirowski et al, envision a system employing a ventricular endocardial electrode and a plate electrode mounted directly to the heart, subcutaneously, or to the skin. However, it was recognized early on that a totally transvenous system would be desirable in order to simplify the use of implantable defibrillators. One such system is suggested in U.S. Pat. No. 3,942,536 by Mirowski et al, which discloses a transvenous lead having electrodes intended for location in the right ventricular apex and superior vena cava. Such systems were eventually tested in human beings, with some success. However, currently available commercial versions of implantable defibrillators typically employ epicardial patch electrodes alone or in conjunction with transvenous electrodes.
While systems employing transvenous endocardial electrodes in combination with epicardial patch electrodes are workable, a thoracotomy is still required in order to apply the epicardial electrode. It is generally believed that it would be highly desirable to produce an implantable defibrillator system which would entirely avoid the necessity of a thoracotomy, and there has been substantial work directed towards such systems, as disclosed in U.S. Pat. No. 4,727,877 issued to Kallok and in U.S. Pat. No. 4,708,145 issued to Tacker et al. Both the Tacker et al and Kallok patents disclose the use of a transvenous, two electrode lead in combination with a subcutaneous patch electrode.
Transvenous ventricular defibrillation electrodes are shown in the above cited Mirowski patents and in the Tacker and Kallok patents cited above. Other endocardial defibrillation electrodes are disclosed in U.S. Pat. No. 4,481,953 issued to Gold et al, U.S. Pat. No. 4,161,952 issued to Kinney et al and U.S. Pat. No. 4,641,656 issued to Smits. The Kinney, Smits, and Kallok patents also disclose transvenous defibrillation electrodes intended for use in or adjacent to the coronary sinus.
Electrode systems comprising only transvenously applied electrodes, or electrodes applied transvenously in conjunction with subcutaneous electrodes are also disclosed in U.S. Pat. No. 4,932,407 issued to Williams on Jun. 12, 1990. This patent is incorporated herein by reference in its entirety and discloses elongated coronary sinus electrodes intended for insertion in the coronary sinus and great vein, for use in conjunction with right ventricular defibrillation electrodes and/or subcutaneous patch electrodes.